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310 Geo-Mar Lett (2008) 28:309–325

records strong seasonal isotope signals (Mannino et al. reflect annual cycles of seasonal temperature fluctuation.
2003; Mannino and Thomas 2007), while oxygen isotopes The study of archaeological seasonality requires the
have been used to provenance the sources of Olivella analysis of large numbers of shells from different strata
biplicata shell beads found in archaeological sites (Eerkens from an archaeological site. To accomplish this, given finite
et al. 2005). resources, it is necessary to design and implement sampling
Many coastal caves across the Mediterranean basin strategies which optimize the numbers of isotope determi-
contain substantial assemblages of shells of marine mol- nations needed (Mannino et al. 2003, 2007; Mannino and
luscs accumulated by human foragers in the Pleistocene Thomas 2007).
(especially in the Upper Palaeolithic) and Holocene To be a useful archive of seawater temperatures, shells
(particularly in the Mesolithic and Neolithic). These should grow continuously through the year and lay down
assemblages are an important source for understanding sufficient shell material in each season to minimise time-
prehistoric human subsistence strategies and past coastal averaging (Shackleton 1973; Bailey et al. 1983). It was
environments. Emiliani et al. (1964) first studied oxygen therefore important to investigate annual patterns of shell
isotopes in marine shells from Mediterranean archaeolog- growth in O. turbinatus.
ical sites, the Haua Fteah cave in Cyrenaica (Libya) and
Arene Candide cave in Liguria (Italy), and noted that
isotope values tracked climate change from the Last Glacial Methods
Maximum into the Holocene. Subsequently, oxygen iso-
topes in marine shells from Mediterranean sites have mostly This study has two discrete but tightly coupled compo-
been used to determine seasons of shellfish collection by nents: shell growth and oxygen isotope thermometry.
human foragers (e.g. Shackleton 1974; Deith and Shackleton
1988; Mannino et al. 2007). Shell growth in O. turbinatus
The topshell Osilinus turbinatus (von Born) is abundant
in prehistoric assemblages and widely distributed in the Mark-recapture experiments were undertaken at two local-
present-day Mediterranean. Oxygen isotope analyses by ities in NW Sicily, San Vito lo Capo and Mazzaforno
Schifano and Censi (1983) suggested it could be a good (Fig. 1), to investigate annual patterns of shell growth.
indicator of palaeoseasonality. Here, we investigate how These rocky shores were selected because they are fairly
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closely oxygen isotopes in shell carbonates (δ O SHELL )of secluded and also have markedly contrasting character-
O. turbinatus reflect present-day sea surface temperatures istics. The limestone shore at San Vito lo Capo has a reef of
(SSTs), to evaluate their potential for reconstructing past vermetids (Dendropoma petraeum) at mean low tide level,
temperature fluctuations and for determining the seasons in while Mazzaforno is one of the few rocky shores in NW
which prehistoric human foragers collected shellfish. For Sicily without a vermetid platform, the metamorphic rocks
the latter, it is not entirely necessary to reconstruct precise plunging straight into the sea. To reduce the disturbance to
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SSTs but it needs to be established that δ O SHELL values shell growth which might be induced by monthly surveys,

Fig. 1 Map of NW Sicily show-
ing the study localities Cala
Grande (on the island of Favig-
nana), Monte Cofano, San Vito
lo Capo and Mazzaforno, and
the marine measuring stations at
Mazara del Vallo and the Gulf of
Palermo. Note: the San Vito lo
Capo locality is southwest of the
town of that name, which lies at
the northern tip of the peninsula